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Human Heart Can Make New CeilsSolving a longstanding （为时甚久的) mystery, scientists have

Human Heart Can Make New Ceils

Solving a longstanding (为时甚久的) mystery, scientists have found that the human heart continues to generate new cardiac (心脏的) cells throughout the life span, although the rate of new cell production slows with age.

The finding, published in the April 3 issue of Science, could open a new path for the treatment of heart diseases such as heart failure and heart attack, experts say.

"We find that the beating cells in the heart, cardiomyocytes (心肌细胞), are renewed," said lead researcher Dr. Jonas Frisen, a professor of stem cell research at the Karolinska Institute in Stockholm, Sweden. "It has previously not been known whether we were limited to the cardiomyocytes we are born with or if they could be renewed," he said.

The process of renewing these cells changes over time, Frisen added. In a 20-year-old, about 1 percent of cardiomyocytes are exchanged each year, but the turnover (更替) rate decreases with age to only 0.45 percent by age 75.

"If we can understand how the generation of new cardiomyocytes is regulated, it may be potentially possible to develop pharmaceuticals (药物) that promote this process to stimulate regeneration after, for example, a heart attack," Frisen said.

That could lead to treatment that helps restore damaged hearts.

"A lot of people suffer from chronic heart failure," noted co-author Dr. Ratan Bhardwaj, also from the Karolinska Institute. "Chronic heart failure arises from heart cells dying," he said.

With this finding, scientists are "opening the door to potential therapies (疗法) to having ourselves heal ourselves," Bhardwaj said. "Maybe one could devise a pharmaceutical agent that would make heart cells make new and more cells to overcome the problem they are facing. "

But barriers remain. According to Bhardwaj, scientists do not yet know how to increase heart cell production to a rate that would replace cells faster than they are dying off, especially in older patients with heart failure. In addition, the number of new cells the heart produces was estimated using healthy hearts -- whether the rate of cell turnover in diseased hearts is the same remains unknown.

The human heart stops producing cardiac cells

A．when a person becomes old.

B．as soon as a person gets sick.

C．immediately after a person is born.

D．once a person dies.

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更多“Human Heart Can Make New Ceils…”相关的问题
第1题
Gene therapy and gene-based drugs are two ways we could benefit from our growing mastery o
f genetic science. But there will be others as well. Here is one of the remarkable therapies on the cutting edge of genetic research that could make their way into mainstream medicine in the coming years.

While it's true that just about every cell in the body has the instructions to make a complete human, most of those instructions are inactivated, and with good reason: the last thing you want for your brain cells is to start churning out stomach acid or your nose to turn into a kidney. The only time cells truly have the potential to turn into any and all body parts is very early in a pregnancy, when so-called stem cells haven't begun to specialize.

Yet this untapped potential could be a terrific boon to medicine. Most diseases involve the death of healthy cells-brain cells in Alzheimer's, cardiac cells in heart disease, pancreatic cells in diabetes, to name a few. If doctors could isolate stem cells, then direct their growth, they might be able to furnish patients with healthy replacement tissue.

It was incredibly difficult, but last fall scientists at the University of Wisconsin managed to isolate stem ceils and get them to grow into neural, gut, muscle and bone cells. The process still can't be controlled, and may have unforeseen limitations; but if efforts to understand and master stem-cell development prove successful, doctors will have a therapeutic tool of incredible power.

The same applies to cloning, which is really just the other side of the coin; true cloning, as first shown with the sheep Dolly two years ago, involves taking a developed cell and reactivating the genome within, resetting its developmental instructions to a pristine state. Once that happens, the rejuvenated cell can develop into a full-fledged animal, genetically identical to its parent.

For agriculture, in which purely physical characteristics like milk production in a cow or low fat in a hog have real market value, biological carbon copies could become routine within a few years. This past year scientists have done for mice and cows what Ian Wilmut did for Dolly, and other creatures are bound to join the cloned menagerie in the coming year.

Human cloning, on the other hand, may be technically feasible but legally and emotionally more difficult. Still, one day it will happen. The ability to reset body cells to a pristine, undeveloped state could give doctors exactly the same advantages they would get from stem cells., the potential to make healthy body tissues of all sorts, and thus to cure disease. That could prove to be a true "miracle cure."

The writer holds that the potential to make healthy body tissues will ______.

A．aggravate moral issues of human cloning

B．bring great benefits to human beings

C．help scientists decode body instructions

D．involve employing surgical instruments

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第2题
SmokingSince 1939, numerous studies have been conducted to determine whether smoking is a

Smoking

Since 1939, numerous studies have been conducted to determine whether smoking is a health hazard. The trend of the evidence has been consistent and indicates that there is a serious health risk. Research teams have conducted studies that show beyond all reasonable doubt that tobacco smoking is associated with a shortened life expectancy.

Cigarette smoking is believed by most research workers in this field to be an important factor in the development of cancer of the lungs and cancer of the throat and is believed to be related to cancer of some other organs of the body. Male cigarette smokers have a higher death rate from heart disease than non-smoking males. Female smokers are thought to be less affected because they do not breathe in the smoke so deeply.

Apart from statistics, it might be helpful to look at what tobacco does to the human body. Smoke is a mixture of gases, vaporized chemicals, minute particles of ash and other solids. There is also nicotine, which is powerful poison, and black tar. As smoke is breathed in, all those components from deposits on the membranes of the lungs. One point of concentration is where the air tube and bronchus divides. Most lung cancer begins at this point.

Filters and low tar tobacco are claimed to make smoking to some extent safer, but they can only slightly reduce, not eliminate the hazards.

It is easy to determine whether smoking is hazardous.

A．Right

B．Wrong

C．Not mentioned

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第3题
Health Care and Epidemics （流行病)Everyone suffers from disease at some time or another.Ho

Health Care and Epidemics (流行病)

Everyone suffers from disease at some time or another. However, millions of people around the world do not have good health care. Sometimes they have no money to pay for medical treatment. Sometimes they have money, but there is no doctor. Sometimes the doctor does not know how to treat the disease, and sometimes there is no treatment. Some people are afraid of doctors. When these conditions are present in large population centers, epidemics can start.

Epidemics can change history. Explorations and wars cause different groups of people to come into contact with other. They carry strange disease to each other. For example, when the Europeans first came to North and South America, they brought diseases with them that killed about 95 percent of the Native American population.

People are very afraid of unknown things, especially diseases. People have all kinds of ideas about how to prevent and treat disease. Some people think that if you eat lots of onions or garlic, you won' t get sick. Others say you should take huge amounts of vitamins. Scientific experiments have not proved most of these theories. However, people still spend millions of dollars on vitamins and other probably useless treatments or preventatives. Some people want antibiotics whenever they get sick. Some antibiotics are very expensive. Much of this money is wasted because some diseases are caused by a virus. Viruses are even smaller than bacteria, and they cause different kinds of diseases. Antibiotics are useless against viruses.

Because of their fear, people can be cruel to victims of disease. Sometimes they fire them from their jobs, throw them out of their apartments, and refuse them transportation services.

In the plague (瘟疫) epidemics a few hundred years ago, people simply covered the doors and windows of the victim' s houses and left them to die inside, all in an effort to protect themselves from getting sick.

Doctors know how most epidemic diseases spread. Some, like tuberculosis, are spread when people' s sneeze (喷嚏) sends the bacteria shooting out into the air. Then they enter the mouth or nose of anyone nearby.

Others are spread through human contact, such as on the hands. When you are sick and blow your nose, you get viruses or bacteria on your hands. Then you touch another person' s hand, and when that person touches his or her mouth, nose, or eyes, the disease enters the body. Some diseases spread when people touch the same dishes, towels, and furniture. You can pick up a disease when you touch things in public buildings.

Other diseases are spread through insects such as flies, mosquitoes, and ticks.

One disease that causes frequent, worldwide epidemics is influenza, or flu for short. The symptoms (症状) of influenza include headache and sometimes a runny nose. Some victims get sick to their stomachs. These symptoms are similar to symptoms of other, milder diseases. Influenza can be a much more serious disease, especially for pregnant women, people over sixty-five, and people already suffering from another disease, such as heart problems. About half of all flu patients have a high body temperature, called a fever. Flu is very contagious. One person catches the flu from another person; it doesn't begin inside the body as heart disease does.

Sometimes medicine can relieve the symptoms. That is, it can make a person cough less, make headaches less intense, and stop noses from running for a while. However, medicine can ' t always cure the disease. So far, there is no cure for many diseases and no medicine to prevent them. People have to try to prevent them in other ways.

Some diseases can be prevented by vaccination (接种疫苗). A liquid vaccine is injected into the arm or taken by mouth and the person is safe from catching that

A．Y

B．N

C．NG

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第4题
Often called the intellectual leader of the animal-rights movement, Regan "is the foremost
philosopher in this country in the field of the moral status of non-rational animals", says Bob Bryan, former chairman of the N.C. State Philosophy and Religion Department. Regan has lectured from Stockholm to Melbourne about the importance of recognizing animals as part of the evolving field of ethics. His books, The Case for Animal Rights and In Defense of Animal Rights, are widely acknowledged as having cemented the roots of the modem animal-rights movement in academia.

To be sure, vegetarianism dates back to Plato and Plutarch. And in America, the first cruelty busts happened in the late 19th century in New York. But society viewed animals largely as properties, until Regan and a handful of other philosophers pushed animal-rights issues into the academic mainstream. Indeed, this academic focus has dramatically altered how Americans approach the ethics of husbandry, some observers say. Once-radical ideas have been firmly woven into society.

Regan envisions a type of "bill of rights" for animals, including the abandonment of pet ownership, elimination of a meat-based diet, and new standards for biomedical research on animals. Essentially, he wants to establish a new kind of solidarity with animals, and stop animal husbandry altogether. "In addition to the visible achievements and changes, there's been what I might call an invisible revolution taking place, and that revolution is the seriousness with which the issue of animal rights is taken in the academy and in higher education," Regan says.

But with Regan planning to retire in December, a growing number of farmers, doctors, and others are questioning the sustainability of his ideas. Increasingly, Americans who feel their rights have become secondary to animals' rights are speaking out against a wave of arson attacks on farmers and pies thrown in the faces of researchers. Radical groups, with sometimes-violent tactics, have been accused of scaring farmers away from speaking up for traditional agrarian values. Indeed, tensions are only rising between animal-rights activists and groups that have traditionally used the land with an eye toward animals' overall welfare, not their "right" to be happy or to live long lives.

The controversy around Regan is heightened by the fact that he's no pacifist. He says he believes it's OK to break the law for a greater purpose. He calls it the "greater-evil doctrine", the idea that there's moral hierarchy to crime. "I think that you can win in court, and that's what I tell people," Regan says. "I don't believe that you should run and hide." The shift in the level of respect has been "seismic", he says. "Contrary to what a lot of people think, there really has been a recognition that there are some things that human beings should not be permitted to do to animals. Where the human heart has grown is in the recognition of what is to be prohibited."

Regan is called the intellectual leader of the animal-rights movement because

A．he is a philosopher in the field of animal-rights protection.

B．he helps to make animal-rights movement an academic subject.

C．he has written many books on how to protect animal rights.

D．he proves that animal societies have their moral standards as human societies do.

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第5题
It is hardly necessary for me to cite all the evidence of the depressing state of literacy
. These figures from the Department of Education are sufficient- 27 million Americans cannot read at all, and a further 35 million read at a level that is less than sufficient to survive in our society.

But my own worry today is less that of the overwhelming problem of elemental literacy than it is of the slightly more luxurious problem of the decline in the skill even of the middle-class reader, of his unwillingness to afford those spaces of silence, those luxuries of domesticity and time and concentration, that surround the image of the classic act of reading, it has been suggested that almost 80 percent of America's literate, educated teenagers can no longer read without an accompanying noise (music) in the background or a television screen flickering at the corner of their field of perception. We know very little about the brain and how it deals with simultaneous conflicting input, but every common-sense intuition suggests we should be profoundly alarmed. This violation of concentration, silence, solitude goes to the very heart of our notion of literacy; this new form. of part-reading, of part-perception against background distraction, renders impossible certain essential acts of apprehension and concentration, let alone that most important tribute any human being can pay to a poem or a piece of prose he or she really loves, which is to learn it by heart. Not by brain, by heart; the expression is vital.

Under these circumstances, the question of what future there is for the arts of reading is a real one. Ahead of us lie technical, psychic, and social transformations probably much more dramatic than those brought about by Gutenberg, the German inventor in printing. The Gutenberg revolution, as we now know it, took a long time; its effects are still being debated. The information revolution will touch every fact of composition, publication, distribution, and reading. No one in the book industry can say with any confidence what will happen to the book as we've known it.

The picture of the reading ability of the American people, drawn by the author, is ______.

A．rather bleak

B．fairly bright

C．very impressive

D．quite encouraging

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第6题
Loneliness has been linked to depression and other health problems. Now, a study says it c
an also spread. A friend of a lonely person was 52% more likely to develop feelings of loneliness. And a friend of that friend was 25% more likely to do the same. Earlier findings showed that happiness, fatness and the ability to stop smoking can also grow like infections within social groups. The findings all come from a major health study in the American town of Framingham, Massachusetts.

The study began in 1948 to investigate the causes of heart disease. Since then, more tests have been added, including measures of loneliness and depression.

The new findings involved more than 5,000 people in the second generation of the Framingham Heart Study. The researchers examined friendship histories and reports of loneliness. The results established a pattern that spread as people reported fewer close friends.

For example, loneliness can affect relationships between next-door neighbors. The loneliness spreads as neighbors who were close friends now spend less time together. The study also found that loneliness spreads more easily among women than men.

Researchers from the University of Chicago, Harvard and the University of California, San Diego, did the study. The findings appeared last month in the Journal of Personality and Social Psychology.

The average person is said to experience feelings of loneliness about 48 days a year. The study found that having a lonely friend can add about 17 days. But every additional friend can decrease loneliness by about 5%, or two and a half days.

Lonely people become less and less trusting of others. This makes it more and more difficult for them to make friends—and more likely that society will reject them.

John Cacioppo at the University of Chicago led the study. He says it is important to recognize and deal with loneliness. He says people who have been pushed to the edges of society should receive help to repair their social networks.

The aim should be to aggressively create what he calls a "protective barrier" against loneliness. This barrier, he says, can keep the whole network from coming apart.

Besides loneliness, which of the following can also spread among people？

A．Friendship.

B．Happiness.

C．Depression.

D．Smoking.

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第7题
选词填空：It's our guilty pleasure: Watching TV is the most common everyday activity, after work and sleep, in many parts of the world

Question 37 to 46 are based on the following passage.

It's our guilty pleasure: Watching TV is the most common everyday activity, after work and sleep, in many parts of the world. Americans view five hours of TV each day, and while we know that spending so much time sitting(37)_____ can lead to obesity(肥胖症)and other disease, researchers have now quantified just how(38)_____ being a couch potato can be.

In an analysis of data from eight large(39)_____ published studies, a Harvard-led group reported in the Journal of the American Medical Association that for every two hours per day spent channel(40)_____, the risk of developing Type 2 diabetes(糖尿病)rose 20% over 8.5 years, the risk of heart disease increased 15% over a(41)_____, and the odds of dying prematurely(42)_____ 13% during a seven-year follow-up. All of these(43)_____ are linked to a lack of physical exercise. But compared with other sedentary(久坐的)activities, like knitting, viewing TV may be especially(44)_____ at promoting unhealthy habits. For one, the sheer number of hours we pass watching TV dwarfs the time we spend on anything else. And other studies have found that watching ads for beer and popcorn may make you more likely to(45)_____ them.

Even so, the authors admit that they didn't compare different sedentary activities to(46)_____ whether TV watching was linked to a greater risk of diabetes, heart disease or early death compared with, say, reading.

A.climbed

B.consume

C.decade

D.determine

E.effective

F.harmful

G.outcomes

H.passively

I.previously

J.resume

K.suffered

L.surfing

M.term

N.terminals

O.twisting

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第8题
It is difficult to imagine what life would be like without memory. The meanings of thousan
ds of everyday perceptions, the bases【B1】the decisions we make, and the roots of our habits and skills are to be【B2】in our past experiences, which are brought into the present【B3】memory.

Memory can be defined as the capacity to keep【B4】available for later use. It includes not only "remembering" thing like arithmetic or historical facts, but also any change in the way an animal typically behaves. Memory is【B5】when a rat gives up eating grain because he has sniffed something suspicious in the grain pile. Memory is also involved when a six year old child learns to swing a baseball bat.

Memory【B6】not only in humans and animals but also in some physical objects and machines. Computers, for example, contain devices for storing data for later use. It is interesting to compare the memory storage capacity of a computer【B7】that of a human being. The instant access memory of a large computer may hold up to 100 000 "words" ready for【B8】use. An average American teenager probably recognizes the meanings of about 100 000 words of English. However, this is but a fraction of the total【B9】of information which the teenager has stored. Consider, for example, the number of facts and places that the teenager can recognize on sight. The use of words is the basis of the advanced problem solving intelligence of human beings. A large part of a person's memory is in terms of words and【B10】of words.

【B1】

A．of

B．to

C．for

D．on

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第9题
Some people might put this question: How useful is walking for your health？Now, the answer

Some people might put this question: How useful is walking for your health？

Now, the answer comes as follows:

Walking is the one of the easiest way to exercise. You can do it almost anywhere and at any time. Walking is also inexpensive. All you need is a pair of comfortable shoes. Walking will give you more energy, make you feel good, help you to relax, reduce stress, help you sleep better, tone your muscles, decrease the risk of death, heart attacks, stroke, some cancers, depression, anxiety and obesity. It improves overall health and lightens your mood. It also helps control your appetite, and increase the number of calories(卡路里) your body uses. For all these masons, people have started walking programs.

Doctors recommend thirty minutes of physical activities (walking or other physical activities) on most days. A fast 30-minute uses 100 calories. You can easily add 30 minutes of exercise daily by making a few minor changes, such as parking farther from work or from a store, then walking the extra distance.

Which is not mentioned as one of the advantages of walking in this passage？

A．It can help you lose weight.

B．It gives you more energy.

C．It's cheap.

D．It helps to increase your appetite.

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第10题
Loneliness has been linked to depression and other health problems. Now, a study says it c
an also spread. A friend of a lonely person was 52% more likely to develop feelings of loneliness. And a friend of that friend was 25% more likely to do the same. Earlier findings showed that happiness, fatness and the ability to stop smoking can also grow like infections within social groups. The findings all come from a major health study in the American town of Framingham, Massachusetts.

The study began in 1948 to investigate the causes of heart disease. Since then, more tests have been added, including measures of loneliness and depression.

The new findings involved more than 5,000 people in the second generation of the Framingham Heart Study. The researchers examined friendship histories and reports of loneliness. The results established a pattern that spread as people reported fewer close friends.

For example, loneliness can affect relationships between next-door neighbors. The loneliness spreads as neighbors who were close friends now spend less time together. The study also found that loneliness spreads more easily among women than men.

Researchers from the University of Chicago, Harvard and the University of California, San Diego, did the study. The findings appeared last month in the Journal of Personality and Social Psychology.

The average person is said to experience feelings of loneliness about 48 days a year. The study found that having a lonely friend can add about 17 days. But every additional friend can decrease loneliness by about 5%, or two and a half days.

Lonely people become less and less trusting of others. This makes it more and more difficult for them to make friends—and more likely that society will reject them.

John Cacioppo at the University of Chicago led the study. He says it is important to recognize and deal with loneliness. He says people who have been pushed to the edges of society should receive help to repair their social networks.

The aim should be to aggressively create what he calls a "protective barrier" against loneliness. This barrier, he says, can keep the whole network from coming apart.

Besides loneliness, which of the following can also spread among people？

A．Friendship.

B．Happiness.

C．Depression.

D．Smoking.

点击查看答案
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